Noiseless Loss Suppression for Entanglement Distribution

TL;DR

This paper extends noiseless loss suppression techniques to entangled states, demonstrating that proper pairing of noiseless amplification and attenuation can restore quantum states after loss, with some states not requiring attenuation.

Contribution

It shows how noiseless amplification and attenuation can be combined to suppress loss in entangled states, clarifying their roles for bipartite and multipartite quantum states.

Findings

Noiseless attenuation is unnecessary for W and NOON states.

Proper pairing of amplification and attenuation restores initial states after loss.

The work distinguishes the entanglement behavior of GHZ and W states.

Abstract

Recent work by Mi\v{c}uda et al. (arXiv:1206.2852v1) suggests that pairing noiseless amplification with noiseless attenuation can conditionally suppress loss terms in the direct transmission of quantum states. Here we extend this work to entangled states: first, we explore bipartite states, specifically the two-mode squeezed vacuum (TMSV) and NOON states; and second, we examine M-partite states, concentrating on W and Greenberger-Horne-Zeilinger (GHZ) states. In analogy with the original proposal, our results demonstrate that in each case under consideration, a correct combination of attenuation and amplification techniques before and after transmission through a pure loss channel can restore the initial quantum state. However, we find that for both W and NOON states, the noiseless attenuation is redundant and not required to achieve loss term suppression. This work clarifies the role of noiseless attenuation when paired with noiseless amplification for entanglement distribution and provides an operational example of how GHZ and W state entanglement differs.